Simple. . . If you got a Discharge send the collector a copy of Schedule F showing that the loan was listed and a copy of your Discharge. Tell the collector to "go away". If attempts to collect continue then reopen your case (assuming you got a Discharge and the case is now closed) and file for a finding of a violation of the discharge injunction.
I would also watch your credit, even though it should never have been sent to collections most places sell portfolios and don't know what they're getting till they have it. It can include accounts that were BK, they might report on your credit as a collection, but that would be inaccurate. I would send the collection agency a notice of the original creditor being included in the BK, and a letter as well. If it's been reported onto your credit make sure you get it deleted. I would also follow up with BBB and CFPB if you can't get any resolution with the collection agency with your letters. I wouldn't necessarily tell them to not send you any mail, since that's how most communicate with people. If you say cease and decist, yet ask for stuff to be deleted etc then they can't send you back a letter stating it was done, which you should keep for your records.